Sealing members are used in a variety of applications to establish fluid seals, such as in valves in a pressurized fluid system. Generally, it is desirable that a sealing member retain its sealing capability over a wide range of operational conditions. It is further generally desirable that a sealing member remain in place when subjected to significant pressurized fluid flow, such as when the sealing member is disposed on a piston member moving from a closed position to an open position.
This phenomena is illustrated in FIGS. 1A-1B, wherein is shown a prior art valve assembly 10 that includes a piston 12, the piston selectively regulating pressurized fluid flow from an inlet port 14. The piston 12 is depicted in its closed position in FIG. 1A, thereby sealing the inlet port 14. In FIG. 1B, the piston 12 is depicted as it transits from the valve closed position to the valve open position.
The fluid flow is sealed in the piston closed position (FIG. 1A) by a conventional O-ring sealing member 16 that presses against the inner wall of the port 14. The sealing member 16 has a circular cross-sectional shape, and is retained on the piston 12 within an annular recess 18. The outer radial surface of the sealing member 16 forms a fluid seal against interior annular sidewall 20 of a housing 22, and an opposing inner radial surface of the sealing member 16 forms a fluid seal against the surface of the annular recess 18.
As the piston 12 moves initially to the piston open position of FIG. 1B, significant fluid flow (arrows 24) can pass adjacent the sealing member 16. Particularly in higher pressure fluid environments, a portion of the fluid can pass between the inner radial surface of the sealing member 16 and the recess 18, exerting an outwardly (or radially) directed force on the sealing member 16. If the hoop strength (the ability to retain its initial hoop shape) of the sealing member 16 is insufficient to resist this outwardly directed force, the sealing member 16 can be deformed and dislocated (blown out) from the annular recess 18, as depicted in FIG. 1B.